Adsorbtion of Total Petroleum Hydrocarbons Contaminated Water with Granular Activated Carbon

This study evaluated the effectiveness of granular activated carbon in treating hydrocarbons contaminated groundwater. Contaminated groundwater samples were obtained from the airfield refueling area of the former Davisville Quonset Point Naval Complex at North Kingstown, R.I. Previous studies on the site showed the contaminants as a mixture of JP 5 and aviation fuel , but because of the changes that might have taken . place within the constituents of the groundwater contaminants due to aging, volatilization, exposure, and interaction with the soils minerals and the groundwater, the contaminants are characterized as Total Petroleum Hydrocarbons(TPH). This study conducted isotherm studies on the contaminated water using Granular Activated Carbon,(GAC) F400, Calgon Corp., Pittsburg, PA. Freundlich Isotherm parameters were obtained from the batch adsorption isothermal studies. The analyses of the breakthrough curves obtained from the experimental column tests provided the information needed to assess the most reasonable GAC adsorber volume for treating the contaminated water under this situation. This could serve as model for sizing a field scale carbon adsorber required for similar contaminants. This study utilized granular activated carbon,(GAC) F400, Calgon in treating 210 Liters of 7 mg/L, 324 Liters of 6 mg/L and 360 Liters of 144 mg/L of aged fuel (TPH) contaminated water samples at flowrates of 0.5 Umin, 0.6 Umin and 0.75 Umin respectively.


ACKNOWLEDGEMENTS
First and foremost, I wish to thank the Almighty God without whom this work could not have been possible and for his magnificent gift of life.
I wish to express my appreciation to Department of Defense for the fellowship granted me. In particular I will like to thank Dr. Daniel W. Urish for his untiring supports.
I wish to thank the U.S Army Corps of Engineers, GZA Inc.,Providence, Rhode -Island and Roy F. Weston Inc. , Manchester, New Hampshire for making it possible to obtain samples for this study.
I also offer my thanks to my major professor, Dr. Calvin Poon for his unrelenting guidance and advice, and Dr. Jim Smith for his advice and encouragement. I like to extend my thanks to the following people, whose assistance have been     (Donaldson,1992).  reported that for over a five year period there were more than 200 hydrocarbon spills in Pennsylvania alone. Widespread use of petroleum products, above ground spills at petrochemicals complexes, overfilling and leakage of underground storage tanks and pipelines, improper underground injection of liquids, leaching from landfills, as well as everyday operations at retail outlets have all contributed to the pollution of soil and groundwater. Groundwater which is the largest potential source of potable water is threatened by innumerable sources of pollution. This pollution has far reaching effects and the cost of groundwater decontamination is tremendous.
Granular Activated Carbon (GAC) has been widely used for water and wastewater treatment. It has proven to be an excellent adsorbent for a broad spectrum of organics. A number of granular activated carbons are commercially available; in this study Calgon Filtrasorb 400 (F-400) was chosen as the carbon of choice because of its proven track record in removing many organic chemicals of concern.
Many mathematical models have been developed to predict adsorption behavior in carbon systems, but the complexity of most systems require the imput of experimental data. Although adsorptive capacity can be evaluated by means of a laboratory test, there is no standard procedure for such tests and there are numerous pitfalls leading to erroneous results and misinterpretation of data.  Incineration of contaminated soil faces similar problems as the ash is considered hazardous and has to be land-filled. Furthermore, excavation can be prohibitive in the presence of underground and above-ground structures, groundwater table and utilities.
Contaminated soils are often contained to prevent the movement of harmful substances going into the groundwater or surrounding soils by erection of slurry formed walls which will either protect the contaminated soil or completely enclose it.
This method requires constant monitoring and long term maintenance. 5 1.2 IN-SITU REMEDIAL TECHNOLOGIES

lAir Stripping
Air stripping is an established technique for removing volatile organic contamination from soils and groundwater. Air stripping has been effectively used to reduce the concentration of taste -and odor -producing compounds and organics.
In air-stripping, toxic chemicals in the liquid phase are transferred to gas phase; and this is done when air is moved through the soil using a series of injection wells, the contaminants volatilize and are displaced from the soil by the injected air. The contaminants are then captured from the soils using extraction pumps and a series of extraction wells.
Henry ' s coefficient is a good indicator of how effectively an organic compound can be removed by air stripping. The greater the Henry ' s coefficient of the compound, the less the volume of air required for stripping the compound from water. The rate at which a volatile compound is removed from water through air stripping depends on the air to water ratio, contact time, available area for mass transfer, temperature of the water and air, physical and chemical properties of the chemical ( Adan1s et al, 1991 ). The removal efficiency or rate can be increased by heating the air to increase the volatilization of the contaminants. The advantages of this method are that it' s simple, relatively inexpensive and can be used to a significant depth in the unsaturated zone. 6

Soil Vapor Extraction
This is a widely used method to remediate subsurface materials contaminated by volatile organic chemicals such as gasoline, jet-fuel and chlorinated solvents.
In this method, soil vapor is drawn to extraction zones through vertical or horizontal well screens where a vacuum is applied. Application of this method is similar to that of air-stripping except that air is pulled through the soil by a vacuum instead of being pushed through . However, this method did not remove low concentration of TPH within a reasonable time when contaminants are a mixtures of volatiles and semi-volatiles, and are located in heterogenous soil media (Choo et al, 1997). This method was used for removing 1700kg of TPH from hydrocarbons contaminated soil and groundwater by the US. Environmental Protection Agency (USEPA) and US.
Coast Guard (USCG) in 1994 at the USCG Support Center in Elizabeth City, North Carolina.

Soil Washing
Soil washing is a promising technology that can be utilized in the treatment of petroleum-hydrocarbon-contaminated soils. As defined by , soil washing is the mechanical or chemical dispersal of contaminated soil in order to dislodge the contaminants from the soil as much as possible. The washing process fractionates the contaminated soils into different particle-sizes fractions (sands, silts and clays) and removes contaminants from the soil by mechanical shearing, dispersion, emulsification, dissolution, air-stripping, froth flotation or a 7 combination of these. After which an appropriate post wash treatment is then applied.

Electro-Osmosis
Electro-osmotic technology (EO) has been used since the 1930's for removing hydrocarbons especially from clays, silts and fine sands. Electro-osmosis has been postulated to induce migration of pesticides, or organics out of contaminated soils (Segall et al, 1980). Electrodes are placed in the contaminated soils; and water is continuously replenished at the anodes. The contaminated pore water will be displaced by the fresh water. This replenishment technique has potential for flushing soluble contaminants from fine grained soils that have low hydraulic conductivities.
Fine grained soils, once contaminated, become a persistent source of leachable hazardous chemicals. Innovative technologies are needed for the decontamination of these tight soils.
For fine soils with low hydraulic conductivities, electro-osmosis can induce flows that would normally require extraordinary or infeasible hydraulic gradients.
Fine grained soils such as clays or silts posses an electrical double layer of negative and positive ions at the solid-liquid interface . The stationary soil particles are negatively charged while the positively charged counter-ions are present in the solution and are mobile. When a direct current (DC) electric field is applied to the moist soil mass, mobile cations migrate to the cathode and the water molecules which hypothetically contain most of the contaminants are dragged along. This way the contaminants are mobilized by EO from within the fine grained soils into the adjacent coarse-grained soils (in-situ) where they could be biologically treated. 8

Vitrification
In-situ vitrification is a method in which the contaminated soil is electrically melted at high temperature and transformed into a chemically inert and stable form of glass. Electrodes placed into the ground are used to heat the soil to a high temperature of about 3600°F which pyrolizes the organics and drives the off-gases to the surface to be contained. The inorganics are trapped within the vitrified glass and thereby rendered immobile. This process is applicable to a wide range of contaminants, including metals and radioactive waste. Because of it's high cost , it's use is restricted to the more troublesome contaminants such as radioactive waste and PCB ' s.

Solvent Extraction
This is a method of removing contaminants from a solid phase by contacting with a non -aqueous fluid that dissolves and mobilizes the contaminants. The fluid is then separated from the solids and reclaimed, thus greatly reducing the concentration of the contaminants in soils.
The commonly used fluids are organic solvents, liquefied gases or supercritical fluids that have affinity for the contaminants in concern. This process involves solubilization of contaminants from the particle pore space, diffusion of contaminants from the solid and washing the extract from the surface of the solids.  have demonstrated that solvent extraction is an effective method for reducing contaminants below the action levels for sediments and soils contaminated with PCB ' s, oil refinery wastes and pesticides. However, contaminated soils with high moisture content have to be de-watered before solvent extraction can be applied on them. 9 1.2.7 Supercritical Fluid Extraction (SFE) The potential environmental threat of the large amount of PCB' s lead to the development of effective PCB' s cleaning techniques. Among these efforts, the use of supercritical fluid extraction for removal of toxic organics from contaminated soils is receiving much attention. This use of SFE in analytical chemistry to replace conventional liquid extraction have been widely reported (Gonasgi et al, 1991) . This is a method in which supercritical fluids with unique properties such as low viscosity, high diffusivity are made to come in contact with the contaminated soils at high pressure and moderate temperature. Small changes in pressure or temperature of the system can cause large changes in the density of the solvent and therefore its ability to solubilize heavy molecular weight and non -volatile waste compounds from the soils. Gonasgi et al ( 1991) reported the success of removing benzene, phenol, p-chlorophenol and m-cresol from aqueous streams by using SC-C0 2 . Following extraction, the waste compound can be completely precipitated from the solvent by means of a drop in pressure to below the solvent's critical conditions. The supercritical fluid' s high diffusivity makes its extraction technique more efficient than those of liquid solvents.

Bioremediation
This is a dynamic method that is used to remove petroleum products such as gasoline, diesel and jet-fuel from the soils and groundwater. Bioremediation as a method is used for removing petroleum hydrocarbons from soil and groundwater by enhancing biodegradation with the addition of either oxygen or nutrients, or both to the contaminated bodies ( Choo et al, 1997).
In biodegradation, micro-organisms use the petroleum hydrocarbons as an energy source, producing carbon-dioxide and water as the end products. Biodegradation occurs either in the presence of dissolved oxygen (aerobic) or without dissolved oxygen(anaerobic). For petroleum hydrocarbons, aerobic biodegradation can occur at faster rates than that of anaerobic biodegradation. With aerobic degradation, oxygen is used along with nutrients such as phosphate and nitrates by the micro-organisms to metabolize the hydrocarbons, while under anaerobic biodegradation, only compounds such as ferric ion, sulfate and nitrate are used, without oxygen. Addition of oxygen, nutrients or both to the contaminated systems stimulate the endemic microbial population resulting in increased bio-mass and enhanced biodegradation.

Carbon Adsorption
Carbon adsorption has been widely used for removing contaminants from water and have been designated a baseline technology for removal of organic contaminants from water. Activated carbon has been widely used for drinking water in United States to control taste and odor.  stated that granular activated carbon (GAC) has proven through many bench I plant I field scale studies to be an effective treatment process for removing a broad spectrum of organics from water.
Randtke et al (1983) wrote that granular activated carbon was an excellent adsorbent for many of the organic contaminants present in water and wastewater discharges.
Its use is often preferred when a significant reduction of organic pollutants, especially those that are non-biodegradable is required. Activated carbon adsorption is based on the ability of specially prepared carbon to remove a wide range of organics from liquid solution by adsorption. The carbon can either be powdered activated carbon (PAC) or granular activated carbon(GAC). The adsorptive properties of the PAC and GAC are similar, since they depend on pore size and the internal surface area of the pore for adsorption. Besides the adsorptive capacity of activated carbon, it also has the ability to withstand thermal reactivation and resistance to attrition losses during transport and handling. The practical application of activated carbon in water and wastewater depend on the reuse of most of the carbon. During use, the carbon gradually becomes saturated with the solute being adsorbed so it eventually losses its capacity to adsorb more contaminants. The ability to be reactivated makes the use of activated carbon economically viable.
(i) Carbon selection There are many commercially available types of activated carbon, each properties that make it more suitable for use in certain applications than others. The initial consideration in the design of any activated carbon system is carbon selection.
The selection of any activated carbon will depend on it's ability to remove the contaminants of concern and meet other system requirements such as pressure drop (head loss), carbon transport, and reactivation. The type of carbon that is most suited for a given application is often determined experimentally by creating an adsorption isotherm. An isotherm study is a laboratory simulation of a batch process in which activated carbon is contacted with a known concentration of the contaminants of concern under continuous mixing until the adsorption reaches equilibrium. The isotherm result will give the measurement required to obtain the Freundlich isotherms.
The Freundlich isotherm is commonly used to determine the carbon adsorptive capacity under the optimal condition.
(ii) Adsorber Configuration In practice, single or multiple adsorbers that are arranged and operated in various configurations to obtain the most efficient use of the activated carbon may be used.
The two basic modes of operation for GAC adsorbers are fixed bed and moving bed.
In a fixed bed, the carbon in the adsorber remains stationary and the flow can be downwards or upwards. In the moving bed adsorber, the carbon expands slightly with an upward flow. Adsorbers can be combined in series or parallel operation depending on the application requirements. Operating columns in series allows complete exhaustion of the first column without releasing significant amount of contaminants in the effluent and removal of the first column for regeneration without distrupting the treatment process, . Parallel adsorber minimizes head loss and requires large total flow-rate. Downward flow enables carbon adsorption to serve as a suspended solids filter as well as an adsorber, though will require back-washing to dislodge and remove suspended solids accumulated on the surface of the bed.
Up-flow adsorbers are preferable for use for high suspended solids concentration because it does not require back-washing.

13
(iii) Effects Of Empty Bed Contact Time Empty Bed Contact time (EBCT) is one of several factors that determine the length of GAC operation before replacement or reactivation. Therefore, in designing an new system, the best EBCT relative to performance criteria and cost is chosen. Longer EBCTs provided more efficient use of GAC, however, beyond a certain EBCT, no apparent advantage will be gained by additional contact time  (iv) Design of activated carbon system 14 additional adsorber volume merely acts as storage capacity for spent carbon.
Therefore, there is an optimum carbon bed depth for the influent understudy from the perspective of adsorber cost alone. The contact time that will be selected for design will be one which yields the most reasonable adsorber volume and reactivation frequency . There is clearly an economic tradeoff between frequency and adsorber volume. Breakthrough depends on the characteristics of both the influent stream and the carbon bed. Different solutes with different carbon will yield different slopes for breakthrough curves at a given contact time. This zone within the carbon bed where the adsorption takes place is referred to as "adsorption zone or mass transfer zone"(MTZ). As more liquid flows through the bed, the adsorption capacity of the upper section of carbon gets exhausted and the adsorption zone moves downward with a gradual increase in the effluent solute concentration. Finally, as the whole bed nears exhaustion, the effluent solute concentration increases rapidly approaching the influent concentration.
Breakthrough curves are very important to the design of an activated carbon column because they define the relationship between the physical-chemical parameters of the solvent-solute-carbon system including the flow-rate, bed size, carbon usage, configuration of columns and the treatment objective. In the design of a granular activated carbon adsorption system, the treatment objective defines the performance needs of the system while the influent characteristics affect the choice of system size and configuration. For a given treatment objective, analysis of several breakthrough curves for the influent of concern provides the information required to size the adsorber.
(v) Column Design Using Scale-Up Approach

Introduction
This study is specifically targeted to evaluate remediation techniques for ajetfuel contaminated site in the former Davisville -Quonset point Naval Complex, North Kingstown, RI . Groundwater samples were obtained from different product recovery wells on the site using hailers. Samples obtained from these recovery wells were mixed together and stored with minimal headspace at room temperature.
The analysis procedures consisted of the following : • The extraction and analysis by gas chromatography (GC) of the contaminated water to determine concentrations of the Total Petroleum Hydrocarbons (TPH) in the water.
• The extraction, analysis and dilution of highly concentrated samples to concentrations similar to that of the true representative of the contaminated ground water.
• Batch adsorption isothermal studies of aged jet fuel/granular activated carbon samples to obtain the Freundlich isotherm parameters.
• The construction of granular activated carbon columns.
• The extraction and analysis of TPH in the influents and effluents from the sampling ports of the activated carbon columns to obtain the breakthrough curves. Analysis of the breakthrough curves to assess the design of the adsorber volume.

Calibration standards
Some of the product recovery wells from which the samples were taken were equipped with filters to separate the contaminants from the groundwater. These contaminants are floating materials that have very little water content in them. In this study, these recovered contaminants are referred to as "free product". The free product of the sample obtained from the site was "dried" using anhydrous sodium sulfate, then placed into a teflon sealed screw cap bottle, stored with minimal headspace in a refrigerator at a temperature of 2°C and used as calibrating standards.

Methodology For Calibrating Standards
A 2 mL vial was weighed, one milliliter of free product was then placed in the vial and re -weighed. The density of the free product was determined using where: p = MN, p is the density of free product.
M is the mass of free product.
V is the volume of free product.
(2.1 ) With the density of free product known, usually 3 mL of carbon disulfide was placed in a 4 mL vial, and 40 uL of free product was added into the solvent and mixed thoroughly. The concentration in mg/mL ofTPH in the solvent was calculated. Dilutions were then made as required.
A minimum of five different concentrations were always used to obtain a calibration curve. One of them was at a concentration near the detection limit and the other concentrations were made to correspond to the expected range of concentrations found in the samples. All the standards were placed in the vials at zero headspace.
The different standards used were analyzed on the same GC using the same analytical conditions indicated above. A minimum of six different prominent chromatogram peaks were picked as representatives for each concentration.
A response factor for each standard was obtained using Where: C is the calculated concentration (mg/rnL) As is the sum of the area absorbance of the selected peaks.
The concentration (mg/rnL) of a sample (TPH) in the solvent was determined using Extracted samples were analyzed the same day they were extracted. 25 (2.4) 2.6 Extraction of Sample Carbon disulfide (5 mL) was added to 250 mL of sample, shaken for 2 minutes, then was allowed to settle, the TPH dissolved in carbon disulfide settled below the water layer. The TPH in carbon disulfide was gently removed from the water layer using a separatory funnel. The carbon disulfide was dried by passing it through a pasteur pipet containing anhydrous sodium sulfate. The carbon disulfide solution was then stored in a vial at zero headspace at 2°C. The method of extraction used for this experiment was tested and proven to achieve a recovery rate of over 70% of the contaminant in the groundwater.

7 Isotherm studies
An isotherm study is a laboratory experiment in which carbon is contacted with a known concentration of solute under continuous stirring and constant temperature until the adsorption reaches equilibrum. The resulting isotherm is the relationship between the amount of substance adsorbed and it's concentration in the surrounding solution.
Prior to it's use, calgon' s Filtrasorb 400 was dried at 130°F for 6 hours and kept in an air tight container until it was ready for use. Five different 160 mL glass bottles were prepared, each containing 10 g of F-400, Calgon granular activated carbon and 150mLof9.2 mg/L, 6.4 mg/L, 5.0 mg/L, 3.5 mg/L, 1.4 mg/L TPH contaminated samples. These were equilibrated for 14 days with constant mixing. Next, samples in each beaker were extracted using carbon disulfide and analyzed on the GC to obtain 26 final concentrations.
The residual of the granular activated carbon in the recovered sample for extraction often heightened the surface tension in the sample when mixed with carbon disulfide such that not all carbon sulfide used for extraction was recovered. Some dissolved in water and some stayed on the surface of the water due to surface tension. However, recovery of TPH in carbon disulfide was made as it settled below the water. The sample with carbon disulfide was mixed and allowed to settle several times, with removal of the TPH in carbon disulfide done several times before a reasonable volume of carbon disulfide with TPH was recovered.        The Fruendlich isot~erm parameters K and 1/n were generated for the aged jet fuels. The data generated was used to determine the Freundlich isotherm parameters for the aged jet fuel/GAC. In the diagram K = XIM. when Ce =1.0, 1/n is the slope of the curve. The best fit isotherm parameters along with the r 2 values are shown in table 3.1. The r 2 which is a measure of the fit of data to isotherm, is 0.9416. The experimental values along with the regression line is shown in Figure 3 .2            For the purpose of using the    The data obtained from this study showed that an aged jet fuel contaminated water can be effectively treated by utilizing granular activated carbon columns.
Exhaustion of GAC in the multiple columns to Ce/Co equals 90% was not accomplished, which necessitated the projection of the data obtained from columns with flowrate of 0.75 Liter/min to achieve Ce/Co% equals 90% and above.
The study confirmed that high influent stream concentration will require high carbon dosage, short contact time will result in early breakthrough and high exhaustion rate. Cost-effective design of a GAC system depends greatly on selection of adsorber type and configuration, EBCT and GAC usage rate .
The fact that x/m obtained from the batch adsorption isotherm test is negligible to that obtained from the GAC column experiments suggests that the GAC columns did not only serve as adsorber but also as a filter. This study also suggests that adsorptive capacity may depend on the initial influent stream concentration.
The Scale-up Approach method of column design requires a greater amount of activated carbon for treating the aged jet fuel contaminated water than the Bed-depth Service Time method. It should be noted that both methods require experiments with field samples and can only be used for a field scale column of like influent characteristics and concentration.
This study could be used as a model for determining the size of a field scale column for treating similar contaminants by applying the same loading rates used in this study.
Also the methodology presented used in this study may be used in evaluating a laboratory column/pilot scale column for other types of contaminants and 54 subsequently a field scale column for such contaminants. 55 5.0 SUGGESTIONS FOR FUTURE WORK Results obtained from analyses of samples from the site showed that there is considerable amount of aged jet fuel in the ground water, the use of a highly complex and highly sensitive instrument for analysis will give a more accurate contamination levels of the groundwater in the various wells.
The data obtained in this study indicated that the use of granular activated carbon column can achieve a high degree of success in remediating the jet fuel contaminated water. More attention should be geared towards a pilot scale/field scale use of GAC columns. Analysis of several breakthrough curves obtained from GAC columns arranged and operated in various configurations could give an improved and more accurate column design.
Availability of resources will encourage scholars and researchers alike and heighten interest into looking for formidable methods of remediation.